The invention relates to a dental device having at least one electrically operable handpiece, the rotational speed of which can be influenced by a control element designed as a pneumatic foot-operated controller, the compressed air present at the output of the pneumatic control element influencing the control of the electric drive.
German published patent application DE 24 17 890 discloses a dental device in which at least one dental handpiece is connected to a compressed-air motor drive fed from a compressed-air source via a compressed-air line. The rotational speed can be changed by means of a control valve, controlling the compressed air, via a pneumatic control device, preferably designed in the form of a foot-operated switch. When using a further handpiece with an electric motor drive, which can be switched on and off via an electrical switching element and the rotational speed of which can be controlled by means of an electric control element, pressure converters are installed which control the compressed air controlled by the control valve for the compressed-air motor drive in such a way that an electric control element of the electric motor drive is influenced. The rotational speed is varied at the electric motor drive via an electric control element taking the form of a sliding contact.
It has be found that, in the case of pneumatic dental appliances which can be influenced in rotational speed by means of foot-operated control, the displacement to be completed at the foot-operated switch to bring about a corresponding change in rotational speed at the dental handpiece is greater at low pressures. However, this only relates to pneumatically operable dental handpieces. At greater pressures, a small change in displacement at the foot-operated switch is already sufficient to bring about a change in the rotational speed at the dental handpiece to be pneumatically operated. The subjective perception of the dentist on which this response is based can only be approximated by a non-linear characteristic, which is therefore also desirable for electrically operable handpieces.
To arrive at a characteristic with such a profile, which cannot be readily realized for example with pressure transducers available for purchase, electronic components (microprocessors, non-linear analog circuits) would therefore have to be used to convert the signal. The dentist would like to operate the electrically operable handpieces likewise with the pneumatic foot-operated control, so that it must be ensured that the rotational speed behavior of the electrically operable handpieces corresponds to the pneumatically operable handpieces, so that the dentist can ideally operate both handpieces by means of his accustomed way of operating the foot-operated control, irrespective of whether a pneumatically operable handpiece or an electrically operable handpiece is concerned.
The invention is based on the object of converting the signal of a pneumatically actuated foot-operated control in such a way that the electrically operable handpieces behave in a way proportional to a pneumatically driven handpiece.
This object is achieved according to the invention by providing that a dental device with at least one electrically operable handpiece, for which it is intended that the rotational speed can be influenced by a foot-operated controller and for which the compressed air downstream of the control element influences the control of the electric drive, is equipped with a graduated filter which is held on a pneumatically actuated hollow body, the graduated filter having formed on it regions which can be sensed by a light barrier generating an electric signal in dependence on the properties of the regions.
With the solution according to the invention, operation both of a pneumatically drivable handpiece and of an electrically drivable handpiece using a foot-operated control shared by both can be brought about, both the response of the pneumatically drivable handpiece and the response of the electrically drivable handpiece being made, by changes in the displacement at the foot-operated switch, to simulate the subjective perception of the dentist approximated best by a non-linear characteristic. Small changes in current intensity, and consequently small changes in rotational speed, at the electrically drivable handpiece can be realized, in the case of low pressures and great displacements at the foot-operated switch, by means of a p/I analog transducer.
In an advantageous way, the graduated filter is designed as a transmission disk. This disk, divided into sectors of different surface finishes, may for example have been provided with a different degree of blackening in each of its three or more sectors. As a result, different optical densities, lying between 0 and 4, can be realized. The degrees of blackening can be brought about for example by using a laser to work on the transmission disk serving as the graduated filter.
In a further refinement of the idea on which the invention is based, the pneumatically actuable hollow body is designed as a hollow spring, to the spindle of which the transmission disk can be fastened. The pneumatically actuable hollow body is part of a p/I analog transducer, the pressure chamber of which may have a connection to the hollow body, which may be designed as a hollow spring. The flexible hollow spring makes it possible to produce a deflection of the graduated filter about its spindle corresponding to the pressure in the p/I transducer. This deflecting movement of the graduated filter is sensed by a light barrier, which encloses the edge, and consequently the sectors provided with different surface finishes, of the graduated filter. Depending on the deflection of the graduated filter about its spindle, the light barrier detects a certain sector region, so that an electric signal corresponding to this sector region can be generated by the light barrier.
A likewise disclosed method of controlling the rotational speeds, on the one hand of an electrically drivable dental handpiece and on the other hand of a pneumatically drivable dental handpiece, which can both be held on a dental appliance and can be regulated in their rotational speed via a shared foot-operated control, comprises the following method steps:
applying the driving-air pressure to the input of the p/I analog transducer,
deflecting a graduated filter by deforming a
sensing the deflection of the graduated filter by a light barrier which is assigned to the latter and generates an electric signal, and
determining the current intensity [1] of the current [I]/pressure [p] characteristic.
By means of the method disclosed according to the invention, the electric drive of the electrically operable handpiece can be controlled via the foot-operated control with a response which corresponds to that of the pneumatically drivable handpiece which can likewise be activated via the foot-operated control.
In the range of driving-air pressures of 0 to 1 bar, the current intensity which can be preset at the electric drive increases proportionately more weakly than in the case of driving-air pressures at the p/I transducer which lie above a pressure of 1 bar.